1. Field of the Invention
The present invention relates to a color filter and a method for fabricating the same, and more particularly, to an inorganic color filter and a method for fabricating the same.
2. Description of the Prior Art
As the development of digital cameras, scanners, and other electronic products progresses, the demand for image sensor increases accordingly. In general, today's image sensors in common usages are divided into two main categories: charge coupled device (CCD) sensors and complementary metal oxide semiconductor image sensors (CMOS image sensors; CIS). The application of CMOS image sensors has been widely adopted for several reasons as described hereinafter. Primarily, CMOS image sensors have advantages such as offering a lower operating voltage, reduced power consumption, and the ability for random access. Additionally, CMOS image sensors are currently capable of integration with the semiconductor fabrication process.
Please refer to FIG. 1, which illustrates a typical structure of a camera system. As shown in FIG. 1, the camera system includes a CMOS image sensor 10, a driving circuit 12, a vertical scan circuit 14, a horizontal scan circuit 16, and an analog front end 18, a signal processing circuit 20, and a control unit 22. The CMOS image sensor 10 includes a plurality of first pixel regions 100a, a plurality of second pixel regions 100b, and a plurality of third pixel regions 100c; and the pixel regions 100a, 100b, 100c are arranged substantially in an array such as the Bayer pattern color filter array. Each pixel region can receive a predetermined wavelength of light respectively, and a charge signal corresponding to the strength of the incident light is generated.
Each first pixel region 100a, each second pixel region 100b, and each third pixel region 100c in FIG. 1 are also designated as R, G, and B, respectively. Namely, each first pixel region 100a is provided with a color filter that transmits light in the red wavelength range; each second pixel region 100b is provided with a color filter that transmits light in the green wavelength range; and each third pixel region 100c is provided with a color filter that transmits light in the blue wavelength range.
The driving circuit 12 drives the vertical scan circuit 14 and the horizontal scan circuit 16 based on a trigger signal from the control unit 22. The vertical scan circuit 14 subsequently activates the pixel regions in the CMOS image sensor 10, thereby making the pixel regions to form charge signal. The vertical scan circuit 14, then, transfers the charge signals in the activated pixel regions to the horizontal scan circuit 16. Using the driving circuit 12, the vertical scan circuit 14 and the horizontal scan circuit 16, the charge signals produced in the pixel regions that are disposed in an array can be converted into voltage signals; and then the voltage signals are outputted to the analog front end 18. The analog front end 18 gathers and amplifies the voltage signals, converts the analog signals into the digital signals, and then outputs the digital signals to the signal processing circuit 20. The signal processing circuit 20, which further includes a matrix-holding unit (not shown), converts the digital signals into a red signal, a green signal, and a blue signal by performing matrix calculations, thereby generating an imaging data.
Please refer to FIG. 2, which is a cross-sectional diagram illustrating the CMOS image sensor 10 in FIG. 1. FIG. 2 merely shows a first pixel region, a second pixel region and a third pixel region. As shown in FIG. 2, The CMOS image sensor 10 is fabricated on a semiconductor substrate 102 such as a silicon substrate. The semiconductor substrate 102 comprises a plurality of first pixel regions 100a, a plurality of second pixel regions 100b, and a plurality of third pixel regions 100c. The semiconductor substrate 102 further comprises a photodiode layer 104; and the photodiode layer 104 comprises a plurality of photodiodes 106, disposed in each first pixel region 100a, each second pixel region 100b, and each third pixel region 100c, respectively, to be used for photoelectric conversions. Generally, photodiode 106 is formed by implanting conductive ions into the semiconductor substrate 102. There is further an insulation layer 108, positioned on the photodiode layer 104, to be used for isolating the photodiode layer 104 and a color filter forming layer 112, which is disposed on the insulator layer 108. Usually, the insulation layer 108 is composed of insulating materials such as silicon oxide. The insulation layer 108 further comprises a plurality of optical shielding layers 110 for preventing interferences caused by light scattered to adjacent pixel regions. Additionally, the color filter forming layer 112 comprises a plurality of color filters 114, which are disposed in each first pixel region 100a, each second pixel region 100b, and each third pixel region 100c, respectively. When an incident light 118 is passed through a micro lens 116 used for providing the focusing, the color filter 114, and the insulation layer 108, the incident light 118 then reaches the photodiode 106; consequently, a corresponding charge signal is thereby generated.
It should be noticed that because conventional color filters are manufactured by mixing organic chemical compounds such as acrylic resin along with pigments or dyestuff of different colors, therefore, the CMOS image sensors made of these organic materials have been facing issues such as degradation due to light exposure and having relatively low heat resistances. Besides, the manufacturing of the conventional color filters, however, requires a troublesome material management process for the pigments or dyestuff of different colors used in the manufacturing process; therefore, this significantly increased the manufacturing costs of the CMOS image sensors.
Accordingly, an inorganic color filter and a method for fabricating the same are provided to improve upon the deficiencies from the conventional organic color filters, for thereby allowing the CMOS image sensors to perform under higher temperature environment.